The present invention is concerned with a new use for certain known bisamidine compounds. It has been discovered that said known compounds possess biological activity as inhibitors of the DNA methyltransferase enzyme and consequently are useful in the treatment of diseases and conditions which involve unregulated differentiation of cells and cellular proceses. The DNA methyltransferase enzyme (EC 2.1.1.37) catalyzes the covalent methylation of the DNA base cytosine at the C5 position of that base. This modification of the base cytosine in a DNA molecule has been shown to play a vital role in the transcriptional inactivation, i.e., silencing of the chromatin as well as in the development and differentiation of cells. The resulting unregulated differentiation of cells and cellular processes is found to be a contributing factor in the development via transformation, and growth of particular cancers and malignancies. The compounds used in the methods of treatment of the present invention hinder the occurrence of the just-described biochemical process and constrain its pathogenic sequelae. As a result, the known compounds of Formula (5.0.0) are useful as chemopreventative and chemotherapeutic agents in the methods of treating cancers, proliferative diseases such as psoriasis, and hyperplasia, which comprise the present invention.